1. Field of the Invention
The present invention relates to the field of computer networking and data communication.
2. Related Art
Problem
Dialogs (also called virtual circuits) carry data between different application processes. Dialogs can be logically set to carry data over a computer network such as a mesh. In a computer network, dialogs provide data communication between application processes running on different end systems or hosts. Dialogs can also carry data between application processes running on the same host.
Multiple functional layers (e.g., Application, Presentation, Session, Transport, Network, Link, and Physical) are used in a data communication network to provide different services and reliability in order to implement virtual circuits (i.e., dialogs). Each layer has an associated protocol and range of primitives to provide services. Each layer forms a corresponding protocol data unit that includes the data and corresponding layer protocol control information. Peer protocol entities at the same layer in different end systems provide services at that layer by managing corresponding layer protocol data units and protocol control information. This operation of multiple functional layers (e.g., Application, Presentation, Session, Transport, Network, Link, and Physical as used in an OSI or Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite) in a data communication network is well-known and need not be described in further detail. See, e.g., Martin, J., TCP/IP Networking: Architecture, Administration, and Programming, (PTR Prentice-Hall: Englewood Cliffs, N.J. 1994), pp. 29-30 (incorporated herein by reference) and F. Halsall, Data Communications, Computer Networks, and Open Systems, 4Ed., (Addison-Wessley: U.S.A. 1996), p. 663 (incorporated herein by reference). Layers are implemented as software, firmware, and/or hardware.
Conventional communication systems now have high bandpass capability. Data throughput for high-speed networking technologies occurs at rates on the order of 100 Megabits/sec to 1 Gigabits/sec. Latency, however, is high. Latency is the time interval between the time a transaction issues and the time the transaction is reported as being completed. In systems with a high latency, the round-trip time for two communicating clients to complete a data request can be on the order of milliseconds.
Latency occurs in conventional communication systems due in part to the overhead involved in the communication layers, including but not limited to, the Transport layer and the layers logically below the Transport layer (e.g., the Network, Link, and Physical layers). However, advancements have been made in lower layer network facilities. The transmission and delivery of messages over some networks is now much more efficient and reliable, especially in closely-coupled, clustered systems.
Transport layer facilities continue to impart substantial latency. Popular transport layer protocols, such as TCP, were developed to support local area and wide-area network (LAN/WAN) environments where the underlying bit rate was moderately high, but reliability was poor, and latency induced by the lower networking layers was high. Transport facilities are included in conventional transport protocols to guarantee reliable transmission and delivery. With the advent of very high-speed, low-latency communication networks like ATM, Fibre Channel, and ServerNet.TM., facilities that were previously incorporated in a Transport Layer to achieve reliable communication, are now being provided by the underlying communication networks themselves. For example, ATM, Fibre Channel, and ServerNet.TM. include specific lower layer facilities for ensuring reliable transmission and delivery, such as, in-order-delivery, check summing, and segmentation and reassembly (SAR).
Conventional high-latency Transport layer protocols and architectures, however, assume lower networking layers (e.g., Network, Link, and Physical layers) are unreliable. Therefore, high-latency transports, such as, the TCP/IP protocol suite, are not positioned to leverage advances in lower-layer data transmission reliability. Conventional transport layer protocols are further limited to a push data model of communication where data is sent regardless of whether a receiver can accommodate the data. Such push model data communication causes flow control problems and excessive data copying.
What is needed is a high-speed, low-latency intraconnect architecture having efficient transport layer processing. A standard transport layer protocol and architecture is needed that can leverage improvements in the reliability of data transmission and delivery, especially for closely-coupled, clustered systems. What is needed is a high-speed, low-latency transport intraconnect architecture that eliminates data copies and provides effective flow control.